Systems and methods for adjusting a congestion window value of a content delivery network

ABSTRACT

Aspects of the present disclosure involve systems, methods, computer program products, and the like, for controlling a congestion window (CWND) value of a communication session of a CDN. In particular, a content server may analyze a request to determine or receive an indication of the type of content being requested. The content server may then set the initial CWND based on the type of content being requested. For example, the content server may set a relatively high CWND value for requested content that is not particularly large, such as image files or text, so that the data of the content is received at the client device quickly. For larger files or files that a have a determined smaller urgency, the initial CWND may be set at a lower value to ensure that providing the data of the content does not congest the link between the devices.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is related to and claims priority under 35 U.S.C. §119(e) from U.S. Patent Application No. 62/414,463, filed Oct. 28, 2016,titled “SYSTEMS AND METHODS FOR ADJUSTING A CONGESTION WINDOW VALUE OF ACONTENT DELIVERY NETWORK,” the entire content of which is incorporatedherein by reference for all purposes.

TECHNICAL FIELD

Aspects of the present disclosure generally relate to content deliverynetworks and more specifically to adjusting or setting a congestionwindow value for a transaction between a client device and a contentserver of the content delivery network for providing content to theclient device.

BACKGROUND

Telecommunication or other types of computer networks provide for thetransmission of information across some distance through terrestrial,wireless or satellite communication networks. Such communications mayinvolve voice, data or multimedia information, among others. Typically,such networks include several servers or other resources from which thecontent or network services can be supplied to a requesting end user.Once a content server of the content delivery network (CDN) is selectedto provide the requested content to a client device, a communicationsession is established between the devices to provide the content to theclient. The communication session may include the exchange ofinformation and/or data included in packets that aid the devices ineffective communication. One such information used by the devicesincludes a congestion window value (otherwise known as the “CWND”). Ingeneral, the CWND is a state variable that limits the amount of datathat can be sent by the transmitting device at any one time. Thisvariable is often used to address congestion on the link between the twocommunicating devices and increase the efficiency of the network.

Network congestion occurs when sent packets from the source (the server)exceed what the destination (the user) or an intermediate network devicecan handle. For example, the destination or client device may includebuffers that store the incoming data or information as the destinationdevice attempts to process the data. In some instances, such as whendata is sent to the receiving device at a rate that the receiving devicecannot process fast enough, the buffers may fill up at the destinationdevice. This can lead to congestion and packet loss, retransmissions,reduced data throughput, performance degradation, and even networkcollapse in extreme cases. In another example, network congestion mayoccur as several devices attempt to communicate over the same link suchthat packets are lost or slow to arrive at the destination device.

In some instances, the destination device may provide an indication ofthe rate at which data may be received. With this information, thecontent server sets an initial CWND and begins providing data packets ofthe requested content to the client device. In response, the clientdevice transmits acknowledgement messages back to the content serverindicating that the transmitting data packets are received. Through ananalysis of the acknowledgement messages, the content server may adjustthe CWND, higher if all of the data packets are correctly received atthe client device or lower if not all of the data packets are received(which indicates congestion on the path between the devices). In thismanner, the communicating devices utilize the CWND to control the rateof transmitted data and information to the client device in response tothe congestion of the communication session.

Typically, the CWND is set by the content server to an initial defaultvalue that is global to the server or to a specific route through thenetwork. However, the default value may either cause congestion on thepath or may not be an efficient transmission rate to provide thecontent. For example, a default initial CWND that is too high mayoverload or congest the path between the devices, particularly ifseveral communication sessions are utilizing the same path. In anotherexample, a default initial CWND may be too cautious in providing thecontent to the client device, resulting in slow start-up times orloading times of the content at the client device.

SUMMARY

One implementation of the present disclosure may take the form of amethod for servicing requests for content in a CDN. The method mayinclude the operations of setting an initial congestion window (CWND)value for a communication session between the client device and thecontent server for providing information to the client device, receivinga request for content at a content server from a client device, therequest comprising an identification of the content, obtaining a contenttype based on the identification of the content from a database ofcontent information, and resetting an initial congestion window (CWND)value for a communication session between the client device and thecontent server based at least on the obtained content type from thedatabase of content information.

Another implementation of the present disclosure may take the form of acontent delivery network (CDN) networking device. The device may includeat least one communication port receiving a request for content from aclient device, the request comprising an identification of the content,a processing device, and computer-readable medium connected to theprocessing device configured to store information and instructions. Theinstructions, when executed, cause the processing device to set aninitial congestion window (CWND) value for a communication session withthe client device providing information to the client device, access adatabase of content information to determine a type of requested contentbased at least on the identification of the content received from theclient device, and reset the initial CWND value for a communicationsession with the client device based at least on the content type fromthe database of content information. The instructions may also cause theprocessing device to provide a portion of the requested content to theclient device over the at least one communication port based at least onthe initial CWND.

Yet another implementation of the present disclosure may take the formof a content delivery network (CDN). The CDN may include a first contentserver configured to set a congestion window (CWND) value for a firstcommunication session between the client device and the first contentserver, control the CWND value during a duration of the firstcommunication session based at least on a detected congestion on aconnection between the client device and the first content server,receive a request for CWND statistics from the client device comprisingone or more controlled CWND values, and transmit the CWND statistics tothe client device. The CDN may also include a second content serverconfigured to receive a request for content at the second content serverfrom the client device, the request comprising an identification of thecontent and the CWND statistics and set an initial CWND value for asecond communication session between the client device and the secondcontent server based at least on the received CWND statistics.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an example network environment for distributing content to anend user from a network, such as a content delivery network (CDN).

FIG. 2A is an example packet flow diagram for establishing acommunication session between a client device and a content server.

FIG. 2B is an example graph illustrating adjusting a congestion windowvalue for the communication session of FIG. 2A over the life of thesession.

FIG. 3 is a flowchart of a method for setting an initial congestionwindow value for providing content to a client device based on the typeof content requested.

FIG. 4 is a flowchart of a method for providing congestion window valuestatistics to a client device for use in other requests for content froma content delivery network.

FIG. 5 is a flowchart of a method for utilizing congestion window valuestatistics and transmission rate information to provide content to aclient of a content delivery network.

FIG. 6 is a diagram illustrating an example of a computing system whichmay be used in implementing embodiments of the present disclosure.

DETAILED DESCRIPTION

Aspects of the present disclosure involve systems, methods, computerprogram products, and the like, for controlling a congestion window(CWND) value of a communication session of a CDN. In one particularembodiment, a CWND value is set by a content server in response toreceiving a request for content from a client device. In thisembodiment, the content server may analyze the request to determine orreceive an indication of the type of content being requested. Thecontent server may then set the initial CWND based on the type ofcontent being requested. For example, the content server may set arelatively high CWND value for requested content that is notparticularly large, such as image files or text, so that the data of thecontent is received at the client device quickly. For larger files orfiles that are less urgent, the initial CWND may be set at a lower valueto ensure that providing the data of the content does not congest thepath between the devices. By utilizing the type of content beingrequested to determine the initial CWND, the CDN may respond to clientdemands and experiences that utilizing a default initial CWND cannotprovide.

In another embodiment, the client device may provide informationconcerning a desired bit rate or transmission rate for a particularrequested content file. The content server may, in turn, set the initialCWND for providing the content to the client device in response to theprovided information. For example, the content server may receive adesired bit rate for streaming a video file at the client device. Withthis information, the content server may set an initial CWND thatattempts to provide the content at the requested bit rate ortransmission speed. Further, the content server may determine that,based on the received information and a measured congestion for thecommunication session, the content may not be provided to the clientdevice at the requested or desired rate. In such as circumstance, thecontent server may notify the client device of the potential forcongestion for the session through one or more messages transmitted tothe client device.

In yet another embodiment, the content server may provide feedbackinformation to the client device concerning the adjustment of the CWNDover the time of the communication session. This information may bestored by the client device for use in other communication sessions withthe CDN. For example, the CWND statistics may be provided to anothercontent server of the CDN by the client device when establishing anothercommunication session. The content server may utilize this informationto set or control the CWND for the communication session. In thismanner, the CWND statistics may provide a roadmap or indication of theperformance capabilities of the client device to aid the content serverin controlling the CWND for the communication session.

FIG. 1 is a network environment 100 for distributing content to one ormore users. Although illustrated in FIG. 1 as a content deliverynetwork, it should be appreciated that aspects of the present disclosuremay apply to any type of telecommunications network that utilizesInternet Protocol (IP) addresses for connecting an end user to one ormore components of the network. For example, aspects of the disclosuremay be utilized to connect a user of the network to an endpoint in thenetwork, a conferencing server, a virtual private network device, andthe like. Thus, although the CDN architecture is used throughout thedocument as the example network architecture through which aspects ofthe present disclosure may be applied; other network architectures andconfigurations are similarly contemplated.

In one implementation of the network environment 100, a CDN 102 iscommunicably coupled to one or more access networks 106. In general, theCDN 102 comprises one or more components configured to provide contentto a user upon a request and an underlying IP network through which therequest is received and the content is provided. The underlying IPnetwork associated with the CDN servers may be of the form of any typeIP-based communication network configured to transmit and receivecommunications through the network and may include any number and typesof telecommunications components. In this manner, CDN-based componentsmay be added to an existing IP-based communication network such that thecomponents receive a request for content, retrieve the content from astorage device, and provide the content to the requesting device throughthe supporting IP network. For simplicity, the use of the term “CDN”throughout this disclosure refers to the combination of the one or morecontent servers and the underlying IP network for processing andtransmitting communications, unless otherwise noted.

In one embodiment, a user device 104 connects to the CDN 102 through oneor more access networks 106 to request and receive content or contentfiles from the CDN. The access network 106 may be under the control ofor operated/maintained by one or more entities, such as, for example,one or more Internet Service Providers (ISPs) that provide access to theCDN 102. Thus, for example, the access network 106 may provide Internetaccess to a user device 104. In addition, the access network 106 mayinclude several connections to the IP network of the CDN 102. Forexample, access network 106 includes access point 120 and access point122. Also, the user device 104 may be connected to any number of accessnetworks 106 such that access to the CDN 102 may occur through anotheraccess network. In general, access to a CDN 102 (or underlying IPnetwork associated with the CDN) may occur through any number of ingressports to the CDN through any number of access networks. In yet anotherembodiment, the user device 104 may be a component of access network106.

The CDN 102 is capable of providing content to a user device 104, whichis generally any form of computing device, such as a personal computer,mobile device, tablet (e.g., iPad), or the like. Content may include,without limitation, videos, multimedia, images, audio files, text,documents, software, and other electronic resources. The user device 104is configured to request, receive, process, and present content. In oneimplementation, the user device 104 includes an Internet browserapplication with which a link (e.g., a hyperlink) to a content item maybe selected or otherwise entered, causing a request to be sent to adirectory server 110 in the CDN 102.

The directory server 110 responds to the request by providing a networkaddress (e.g., an IP address) where the content associated with theselected link can be obtained. In one implementation, the directoryserver 110 provides a domain name system (DNS) service, which resolvesan alphanumeric domain name to an IP address. The directory server 110resolves the link name (e.g., URL or other identifier) to an associatednetwork address from which the user device 104 can retrieve the content.The operation of the directory server 110 and access network 106 toresolve requests for content from the user device 104 is discussed inmore detail below with reference to FIG. 2.

In one implementation, the CDN 102 includes an edge server 112, whichmay cache content from another server to make it available in a moregeographically or logically proximate location to the user device 104.The edge server 112 may reduce network loads, optimize utilization ofavailable capacity, lower delivery costs, and/or reduce content downloadtime. The edge server 112 is configured to provide requested content toa requestor, which may be the user device 104 possibly via anintermediate device, for example, in the access network 106. In oneimplementation, the edge server 112 provides the requested content thatis locally stored in cache. In another implementation, the edge server112 retrieves the requested content from another source, such as a mediaaccess server (MAS) (e.g., a content distribution server 114 or acontent origin server 116 of a content provider network 118). Thecontent is then served to the user device 104 in response to therequests.

In one implementation, a user of the user computing device 104 enters alink name (e.g., URL or other identifier) into a browser executed on thecomputing device. The link name is associated with a network addresswithin the CDN 102 at which the content may be obtained and provided tothe computing device. For example, the user or the user device may entera URL such as www.examplecom/content into the browser of the computingdevice 104. Upon entering the URL, the hostname may be extracted by thebrowser (www.example.com in this particular case) and sends a request(possibly via an operating system running within the computing device104) to a domain name server (DNS) associated with the user's accessnetwork 106.

Once a content server is selected, the client device 104 may connect tothe selected content server 112 to begin receiving the content. In otherwords, the client device 104 utilizes the IP address of the contentserver 112 received from the DNS resolver 110 to establish acommunication session with the content server to begin receiving thecontent. FIG. 2A is an example packet flow diagram for establishing acommunication session between a client device 104 and a content server112. The packets illustrated may be just a few of the packets that aretransmitted between the devices to establish a communication session totransfer content to the client device 104. Other packets not shown ordiscussed may be exchanged, as will be understood by those of skill inthe art.

FIG. 2A includes a left column 202 that includes the packets originatingat the client device 104 that are transmitted to the content server 112.Similarly, a right column 204 includes packets originating at thecontent server 112 that are transmitted to the client device 104. Theduration of the communication session is illustrated along the verticalaxis of the graph 200 of FIG. 2A such that packets illustrated at thetop of the graph are transmitted at the beginning of the communicationsession, followed by the packets moving down through the graph. Thus,after the client device 104 receives an IP address of the content server112 (as provided by the CDN 102), the client device transmits a SYN(synchronize) packet 206 to the IP address of the content server. In oneparticular embodiment, the devices utilize a transmission controlprotocol (TCP) communication standard to communicate. However, it shouldbe appreciated that the devices may utilize any communication standardto communicate and exchange communication packets.

In general, the SYN packet 206 instructs the content server 112 that theclient device 104 intends on communicating. The content server 112 may,in response, transmit a SYN acknowledgement message 208 back to theclient device 104 indicating that the content server is ready tocommunicate with the client device. Upon receiving the acknowledgementmessage 208, the client device 104 may transmit its own acknowledgementmessage 210 followed by a first request 212 for content from the contentserver 112. Further, the client device 104 may establish a maximum CWNDvalue in the ACK message 210. In other words, the ACK message 210includes a window size for content that the client device 104 is able toreceive. Upon receipt at the content server 112, the initial CWND valuefor the communication session is established by the content server.Thus, the initial CWND is established prior to receiving any indicationof the content being requested by the client device 104. In general, theinitial CWND value is set by the content server 112 based on a defaultCWND value utilized by the content server for all or some communicationsessions.

Once the request 212 for the data is received, the content server 112returns an acknowledgement and the first portion of the content data 214to the client device 104. The client device 104 responds with an ACKmessage 216 and requests the next packet of content data from thecontent server 112. In this manner, the client device 104 and thecontent server 112 may continue to exchange requests for data and thecontent data to provide the requested content to the client device.Further, as shown in FIG. 2B, the CWND value for the communicationsession may be adjusted by content server 112 to provide the content tothe client device 104 at a faster rate to improve the performance of theCDN network 102.

In particular, FIG. 2B is an example graph illustrating adjusting acongestion window value for the communication session of FIG. 2A overthe life of the session. In the graph 250, an example CWND value of acommunication session between two networking devices is plotted overtime (the CWND value plotted along the y-axis and time plotted along thex-axis). As shown, the CWND value for the communication session beginsat an initial value 252. This initial value may be set by the contentserver 112 based on the acknowledgement message 210 described above. Inother words, the content server 112 sets the initial CWND value thatcontrols the rate that the content is transmitted to the client device104. More particularly, the CWND value limits the amount of content datatransmitted to the client device 104 before the content server receivesan acknowledgement message from the client device that at least some ofthe transmitted content data is correctly received. Once anacknowledgement message is received by the content server 112,additional content data may be transmitted to the client device 104,again limited by the CWND value.

In some instances, the content server 112 and/or the client device 104may adjust the CWND during the communication session. For example and asshown in the graph 250, the CWND value begins at the initial value 252and is increased by the content server 112. The setting of the CWND atthe initial value 252 may be set at a relatively low value to ensurethat the client device 104 can adequately receive the content data andto avoid overloading the devices or transmission devices between thecommunicating devices. Further, the CWND value may be increased duringthe communication session to provide the content data at a faster rateto maximize providing the data to the client device 104.

At some point, one or more of the communicating devices may detectcongestion between the devices. For example, the content server 112 maynot receive the acknowledgement message from the client device 104indicating that the client device has not received all of thetransmitted content data because of the congestion. Once congestion isdetected, the content server 112 (or client device 104) may adjust theCWND value down to slow down the transmission of content data to theclient device, as shown in the graph 250 at time 254. At this time 254,the CWND for the session is adjusted down to ensure that the transmittedcontent data is received at the client device 104 through the detectedcongestion. The CWND value at time 254 may be any value determined bythe content server 112, but may include a CWND value at which theacknowledgement message from the client device 104 is received.

Following the adjustment of the CWND in response to the congestion, theCWND value may again begin to be adjusted up to provide the content dataat a faster rate. This may continue until congestion is again detected,at which point the CWND value is adjusted down. This process ofincreasing the CWND value for the session until congestion is detectedmay continue for the entirety of the communication session to providethe content data to the client device, resulting in the sawtooth patternof the graph 250 of FIG. 2B. However, it should be appreciated that theCWND value of a communication session may be adjusted in any manner inresponse to a detected congestion between the communicating devices,including sharper or less increases, less sharp decreases, increasing ordecreasing in a stepping manner, and the like.

The adjustment of the CWND value of a communication session may not,however, provide the most efficient method of providing the content datato the client device 104. In some instances, the adjustment of the CWNDmay increase the likelihood of congestion experienced by the devices andother devices utilizing the same network. To improve the operation andefficiency of a CDN and/or networking device, other mechanisms forsetting and controlling a CWND value (or any other value that limits therate of providing content to a requesting device) is now discussed. Inparticular, FIG. 3 is a flowchart of a method 300 for setting an initialcongestion window value for providing content to a client device basedon the type of content requested. In general, the operations of themethod 300 may be performed by any networking device or combination ofdevices. In one particular implementation, the operations are performedby a content server providing content data to a client device based on arequest for the content.

Beginning in operation 302, the content server receives asynchronization message to initiate or otherwise create a communicationsession with a requesting device. In one instance, the synchronizationmessage is transmitted by a client device 104 to a content server 112after the client device receives an IP address for the content serverfrom a DNS of a CDN. The synchronization message may requestsynchronization utilizing any known or hereafter developed communicationprotocol, such as a TCP communication session. One example of asynchronization message is discussed above with relation to FIG. 2.

Also discussed above, the content server 112 may transmit asynchronization acknowledgement message in response to receiving thesynchronization message in operation 304. Once the devices are synched,the content server receives an acknowledgement message with a windowbuffer size value of the client device in operation 306. This messagewith the window buffer size is also discussed above. However, ratherthan setting an initial CWND value for the session between the devicesbased on a default value for the content server, the content server maywait until a request for content data is received in operation 308. Ingeneral, the request for content data may include some type ofidentification of the content, such as a content file name. With theidentifying information, the content server may determine a type of therequested content. For example, in operation 310, the content server mayretrieve a content type from a database based on the identification ofthe requested content. Based on the content type, the content server mayset the initial CWND in operation 312.

Content requested from and provided by the content server may includevarious types of content of various size files. For example, therequested content may be a simple thumbnail icon of a website ofrelatively small size up to a request for a high-definition video fileof a relatively large size. Aspects or information about all or some ofthe content available from the content server may be stored andcataloged in a database of content files. In general, any informationabout the content available through the content server may be stored inthe database. In one embodiment, the information about the content filesis organized in the database based on a content identifier, such as acontent file name. Once received, the content server may utilize thecontent file identifier to obtain the content information, including thefile size.

With the content file information retrieved, the content server may setthe initial CWND for the communication session accordingly. For example,the content server may determine that a small content file (such as athumbnail icon) may be transmitted to the client device quickly withoutcausing a large amount of congestion on the connection between thedevices. In this example, the content server may set the CWND at a highvalue to get the content file to the client device quickly. In anotherexample, the content server may determine that a large content file(such as a video file) may be transmitted to the client device slowly soas not to initially overwhelm the connection between the devices andcause undue congestion on the connection. Thus, the content server mayset the CWND at a lower value to “test” the connection between thedevices and ensure that providing the content will not overload theconnection or the receiving device. The determination to set the initialCWND at a lower value may also be based on the length of time it willtake to provide the entire content file. In other words, because it willtake some time to provide the entire video file to the client device,there is time for the CWND value to be adjusted to account forcongestion through the entire communication session. Smaller contentfiles, like image files or text files, may be transmitted fully in ashort amount of time such that it may be too cautious to set the initialCWND value low. In general, any consideration for providing the contentfile to the client device may be utilized by the content server whensetting the initial CWND value based on the identification of thecontent file from the database. Other considerations are discussed inmore detail below.

Regardless of the initial CWND value set by the content server, theserver may wait until the request for the content and the identificationof the content is received before setting the initial value. Once set,the content server may begin transmitting the content data to the clientdevice based at least in part on the initial CWND value in operation314. Further, in operation 316, the CWND value may be adjusted based ona determination of congestion in the communication session, as describedabove with relation to FIG. 2B. In this manner, the content server mayset the initial value of the CWND based on a content type rather than toa default initial value.

Some transmission protocols, such as but not limited to, Transport LayerSecurity (TLS) may utilize an additional exchange of information (suchas encryption key exchange) prior to the transmission of the request. Inthese protocols that utilize an additional exchange, an interim initialCWND may be chosen to facilitate this exchange and may be reset at thetime of the request based on any of the methods described herein forsetting the initial CWND. For simplicity, this is still referred toherein as the initial CWND. Further, multiple requests may occurserially in a single protocol connection. For example, a single sessionbetween a client device and a content server may include requests forseveral types of content, such as requests for images, requests fortext, requests for videos, etc. to present a webpage to a user of theclient device. In these instances, the congestion window may be reset asdescribed for the initial CWND when a new request is received over theexisting connection. For simplicity, this is also referred to herein asthe initial CWND.

As mentioned, there may be various considerations for setting theinitial CWND value based on the identification of the requested contentby the content server. For example and as mentioned above, a larger filemay have time during the communication session to find the proper windowsize to provide the content in the most efficient manner to the clientdevice without causing undue congestion on the network. However, smallercontent files may not have enough time to locate the most efficientwindow size for content data. Further, because the content file size issmall, the entire file may be provided with little interruption to thenetwork such that the smaller content file may be provided faster to arequesting device than previous CWND setting schemes. This provides amore pleasant experience for a requester of content as the content maybe received faster.

In another example, the content server may consider the time sensitivityof the content file when setting the initial CWND value. For example,based on the content identifier and information stored in the database,the content server may determine that the content file does not need tobe provided at an optimum speed to the client device. This may be thecase for content files that are being downloaded, but will beexperienced by a user of the client device at a later time, such asdownloading computer software updates or entertainment files that willbe experienced at a later time. In contrast, content files that aredeemed to be time-sensitive may have an initial higher CWND value toensure that the content file is provided as fast as possible on thenetwork without disruption of the operations of the network. In asimilar manner, the adjustment of the CWND value over the duration ofthe communication session may be also based on the content fileinformation stored in the database. For example, a less time-sensitivefile may be adjusted upward more slowly than a content file that shouldbe received at the client device as soon as possible by the network. Ingeneral, the setting and control of the CWND value may be based on anyinformation in the database and for any business or efficiency rule ofthe network as determined by an administrator of the telecommunicationsnetwork.

In still another embodiment, the content server may obtain informationabout the performance capabilities of the client device and/or therequested content and set or control the CWND value accordingly. Forexample, FIG. 4 is a flowchart of a method 400 for providing congestionwindow value statistics to a client device for use in other requests forcontent from a content delivery network. Similar to above, theoperations of the method 400 of FIG. 4 may be performed by a contentserver, any networking devices, and/or collection of networking devices.

Beginning in operation 402, the content server receives the request forcontent from a client device and, in operation 404, retrieves thecontent type from the database, as explained above. In operation 406,the content server may determine a feature of the requested contenttype. For example, the request received at the content server may be fora streaming live video feed to be provided to the client device. In someinstances, the live video feed may include high definition video and/oraudio. The particular features of the requested content may be storedand accessible through the content type database described above. Withthe content information obtained, the content server may determine therate at which the content data should be provided to the client deviceto maintain the particular features of the content file.

In operation 408, the content server may determine a latency value inproviding data to the client device over the network connection. Thislatency value may be determined at the client device by comparing atimestamp included in a data packet transmitted to the client device tothe time that the packet is received. In another example, the clientdevice may return an acknowledgement message to the content server for aparticular content packet, which the content server may utilize tocalculate an estimated latency value for providing data to the clientdevice. Further, in operation 410, the content server receives anadvertised congestion window from the client device, described above inthe acknowledgement message 210 transmitted to the content server inFIG. 2A.

With the obtained features of the content file, the estimated latency tothe client device, and the available congestion window of the clientdevice, the content server may calculate and set an initial CWND valuebased on one or more calculations in operation 412. In particular, thecontent server may calculate a minimum CWND value needed to provide thecontent to the client device to meet the content file features and setthe initial CWND value accordingly. Further, the content server maycontrol the adjustment of the CWND value in a similar manner based onthe calculations. Further still, the content server may determine that,based on the client device characteristics and the estimated latency,the content cannot be provided to the client within the specificationsof the content file. In such a circumstance, the content server maynotify the client device and/or a network administrator accordingly.

In one particular example for live video, it may improve the user'sexperience receiving the content file if the startup time for the videois reduced. To reduce the startup time, the buffer window and thepossible bitrate of the client device may be determined and, if theclient device can process a high bitrate and/or has a large buffer, arelatively large initial CWND value may be set by the content server.This high initial CWND value may provide an initial blast of contentdata to the client device to get the live video started quickly. Inanother example, when the content server determines that the videostream cannot be supported by the client device or there is too muchcongestion on the connection to provide the content at thespecifications of the video, the content server notifies the clientdevice. This notification may occur prior to the client device emptyingits buffer so that the client device may adjust the playback of the dataaccordingly and there is no interruption to the content presentation.The adjustment of the CWND may also be based on these calculations toensure that congestion on the connection is likely to not impede thetransmission of the content data to the client device.

In another embodiment, the content server, upon determining that a videostream cannot be supported by the client device or that there is toomuch congestion on the connection to provide the content at thespecifications of the video, may provide alternative content (perhaps ata lower bitrate) to the client device. Conversely, if it is determinedthat the network and client device may support a higher rate, a higherbit rate file may be substituted in the session and provided to theclient device.

In yet another embodiment, one or more CWND statistics for thecommunication session (or multiple communication sessions) may beprovided to the client device for use in other requests for content. Forexample, FIG. 5 is a flowchart of a method 500 for utilizing congestionwindow value statistics and transmission rate information to providecontent to a client of a content delivery network. The CWND statisticsand transmission rate information may be provided by a content server(or other device or devices of the network) to the client device andstored by the client device. As such, the operations of the method 500may be performed by a content device or other network device orcombination of devices of a CDN.

Beginning in operation 502, the content server receives a request from aclient device for CWND statistics at the end or near the end of acommunication session between the devices. The request for the CWNDstatistics may be included in a header of a packet message transmittedbetween the devices or may be included as a separate request to thecontent server. In response, the content server may transmit the CWNDstatistics calculated by the content server. For example, the contentserver may maintain running statistics on the CWND values of thecommunication session with the client device. Certain aspects of thecalculated statistics may be of particular use by the client device,such as a maximum CWND value reached during the session, a minimum CWNDvalue, an average CWND value, the last CWND value of the session, andthe like. In general, any information about the CWND values utilizedduring the communication session may be gathered and provided by thecontent server. In some implementations, the content server may send theactual statistical data, encrypted statistical data, or a lookup keyused to retrieve store statistical information from a database. As such,in operation 504 one or more of the calculated values may be transmittedto the client device.

As mentioned above, the client device may store the received CWNDstatistics. In some instances, this information may also be utilized bythe client device when requesting additional content from the contentserver or from another content server of the CDN or another CDN. Toutilize the CWND statistic information, the client device may transmit arequest for additional or new content data from the content server suchthat the content server receives the request in operation 506. It shouldbe appreciated that the content server that receives the request foradditional content may be the same content server that provided the CWNDstatistics to the client device or may be another content server (or anyother network device). Further, the client device may also provide thestored CWND statistics from the previous communication session to thecontent server in operation 508. In one particular embodiment, thecontent server may request the CWND statistics from the client deviceonce a request for content is received, such as through a GETSTATcommand or request. Further and as explained in more detail below, thecontent server may utilize the CWND statistics received to set andcontrol the CWND for the communication session with the requestingclient device in operation 510.

In general, the content server may utilize the CWND statistics from aprevious communication session to gain some information about therequesting client device and possible congestion between thecommunicating devices and/or control the CWND values during the session.For example, the content server may set the initial CWND value fortransferring content data to the client device at the last known CWNDvalue or the minimum value to make it more likely that the first packetsof content data are received by the client device. In another example,the content server may control the adjustment of the CWND value based onthe statistics, such as quickly bringing the CWND to the receivedaverage CWND value. In yet another example, the content server may limitthe rate the data is sent to the client device based on the receivedCWND statistics, regardless of the advertised bit rates from the clientdevice.

Further, other information included in the CWND statistics may aid thecontent server in providing the requested data. For example, the CWNDstatistics provided by the client device may indicate timestamps,geographic locations, and/or device types of a previous content serverfrom which the statistics are received. If, for example, the currentcontent server determines that the information of the previous contentserver is substantially different than the current content server, thecontent server may disregard the statistics from the previouscommunication session. For example, if the previous content server wasof a different type or is located in a vastly different geographiclocation, the received statistics may not apply to the currentcommunication session. However, if the specifications of the previouscontent server are similar to the current content server, the CWNDstatistics may be considered and used during CWND control.

The CWND control of a content server of a CDN may also be utilizedthrough the network. For example, one or more content servers of a CDNmay attempt different schemes for controlling the CWND value duringcommunication sessions with client devices. These schemes may be chosenrandomly from a database of CWND schemes. The effectiveness of eachscheme may be tracked by the content server and stored in a centraldatabase. Through the iterations of the schemes as applied by thevarious content servers of the CDN, the overall performance of theschemes may be understood and tracked by the CDN to maximize theeffectiveness of providing the content to the client device. Theapplication of one or more of the control schemes to the content serversof the CDN may be based on any criteria, such as speed or overall impactto the network on providing the content.

Through the systems and methods described above, the CWND value of acommunication session may be set and controlled to provide a moreefficient delivery of content to the client device. In particular, aninitial CWND value may be set by a content server based on a type ofcontent requested, rather than to a default value for the contentserver. Further, control of the CWND value during the communicationsession may be based on one or more CWND value statistics provided tothe content server by the client device indicating a previouscommunication session. Through these schemes, the CWND value may becontrolled by the content server more closely to maximize the efficiency(or based on another other performance or business rule) when providingcontent from a CDN to a client device.

FIG. 6 is a block diagram illustrating an example of a computing deviceor computer system 600 which may be used in implementing the embodimentsof the network disclosed above. In particular, the computing device ofFIG. 6 is one embodiment of the server or other networking componentthat performs one of more of the operations described above. Thecomputer system (system) includes one or more processors 602-606.Processors 602-606 may include one or more internal levels of cache (notshown) and a bus controller or bus interface unit to direct interactionwith the processor bus 612. Processor bus 612, also known as the hostbus or the front side bus, may be used to couple the processors 602-606with the system interface 614. System interface 614 may be connected tothe processor bus 612 to interface other components of the system 600with the processor bus 612. For example, system interface 614 mayinclude a memory controller 618 for interfacing a main memory 616 withthe processor bus 612. The main memory 616 typically includes one ormore memory cards and a control circuit (not shown). System interface614 may also include an input/output (I/O) interface 620 to interfaceone or more I/O bridges or I/O devices with the processor bus 612. Oneor more I/O controllers and/or I/O devices may be connected with the I/Obus 626, such as I/O controller 628 and I/O device 630, as illustrated.

I/O device 630 may also include an input device (not shown), such as analphanumeric input device, including alphanumeric and other keys forcommunicating information and/or command selections to the processors602-606. Another type of user input device includes cursor control, suchas a mouse, a trackball, or cursor direction keys for communicatingdirection information and command selections to the processors 602-606and for controlling cursor movement on the display device.

System 600 may include a dynamic storage device, referred to as mainmemory 616, or a random access memory (RAM) or other computer-readabledevices coupled to the processor bus 612 for storing information andinstructions to be executed by the processors 602-606. Main memory 616also may be used for storing temporary variables or other intermediateinformation during execution of instructions by the processors 602-606.System 600 may include a read only memory (ROM) and/or other staticstorage device coupled to the processor bus 612 for storing staticinformation and instructions for the processors 602-606. The system setforth in FIG. 6 is but one possible example of a computer system thatmay employ or be configured in accordance with aspects of the presentdisclosure.

According to one embodiment, the above techniques may be performed bycomputer system 600 in response to processor 604 executing one or moresequences of one or more instructions contained in main memory 616.These instructions may be read into main memory 616 from anothermachine-readable medium, such as a storage device. Execution of thesequences of instructions contained in main memory 616 may causeprocessors 602-606 to perform the process steps described herein. Inalternative embodiments, circuitry may be used in place of or incombination with the software instructions. Thus, embodiments of thepresent disclosure may include both hardware and software components.

A machine readable medium includes any mechanism for storing ortransmitting information in a form (e.g., software, processingapplication) readable by a machine (e.g., a computer). Such media maytake the form of, but is not limited to, non-volatile media and volatilemedia. Non-volatile media includes optical or magnetic disks. Volatilemedia includes dynamic memory, such as main memory 616. Common forms ofmachine-readable medium may include, but is not limited to, magneticstorage medium (e.g., floppy diskette); optical storage medium (e.g.,CD-ROM); magneto-optical storage medium; read only memory (ROM); randomaccess memory (RAM); erasable programmable memory (e.g., EPROM andEEPROM); flash memory; or other types of medium suitable for storingelectronic instructions.

Embodiments of the present disclosure include various steps, which aredescribed in this specification. The steps may be performed by hardwarecomponents or may be embodied in machine-executable instructions, whichmay be used to cause a general-purpose or special-purpose processorprogrammed with the instructions to perform the steps. Alternatively,the steps may be performed by a combination of hardware, software and/orfirmware.

Various modifications and additions can be made to the exemplaryembodiments discussed without departing from the scope of the presentinvention. For example, while the embodiments described above refer toparticular features, the scope of this invention also includesembodiments having different combinations of features and embodimentsthat do not include all of the described features. Accordingly, thescope of the present invention is intended to embrace all suchalternatives, modifications, and variations together with allequivalents thereof.

We claim:
 1. A method for servicing requests for content in a CDN, themethod comprising: setting an initial congestion window (CWND) value fora communication session between the client device and the content serverfor providing information to the client device; receiving a request forcontent at a content server from a client device, the request comprisingan identification of the content; obtaining a content type based on theidentification of the content from a database of content information;and resetting the initial CWND value for a communication session betweenthe client device and the content server based at least on the obtainedcontent type from the database of content information.
 2. The method ofclaim 1 further comprising: detecting a congestion on a connectionbetween the client device and the content server; and adjusting theinitial CWND based on the detected congestion on the connection;
 3. Themethod of claim 1 wherein the identification of the content comprises acontent file name included in the request for the content.
 4. The methodof claim 1 wherein the content type obtained from the database comprisesa file size of the requested content.
 5. The method of claim 1 whereinthe content type obtained from the database comprises an estimatedurgency of receiving the requested content for the client device.
 6. Themethod of claim 1 wherein the identification of the content comprises arequested bit rate for receiving the content from the content server atthe client device.
 7. The method of claim 2 further comprising:receiving a request for CWND statistics from the client devicecomprising one or more calculated CWND values set by the content serverduring the communication session; and transmitting the CWND statisticsto the client device.
 8. The method of claim 7 wherein the CWNDstatistics comprise at least one of a maximum CWND value, a minimum CWNDvalue, an average CWND value, and a last of a CWND value.
 9. The methodof claim 7 further comprising: receiving a second request for content ata second content server from the client device, the second requestcomprising an identification of the content and the CWND statistics;setting an initial congestion window (CWND) value for a secondcommunication session between the client device and the second contentserver based at least on the received CWND statistics.
 10. A contentdelivery network (CDN) networking device comprising: at least onecommunication port for receiving a request for content from a clientdevice, the request comprising an identification of the content; aprocessing device; and a computer-readable medium connected to theprocessing device configured to store information and instructions that,when executed by the processing device, performs the operations of:setting an initial congestion window (CWND) value for a communicationsession with the client device providing information to the clientdevice; accessing a database of content information to determine a typeof requested content based at least on the identification of the contentreceived from the client device; resetting the initial CWND value forthe communication session with the client device based at least on thecontent type from the database of content information; and providing aportion of the requested content to the client device over the at leastone communication port based at least on the reset initial CWND.
 11. TheCDN device of claim 10, wherein the processing device further performsthe operations of: detecting a congestion on a connection associatedwith the communication session; and adjusting the initial CWND based onthe detected congestion on the connection;
 12. The CDN device of claim10 wherein the identification of the content comprises a content filename included in the request for the content.
 13. The CDN device ofclaim 10 wherein the content type determined from the database comprisesa file size of the requested content.
 14. The CDN device of claim 10wherein the content type determined from the database comprises anestimated urgency of receiving the requested content for the clientdevice.
 15. The CDN device of claim 10 wherein the identification of thecontent comprises a requested bit rate for receiving the content at theclient device.
 16. The CDN device of claim 10, wherein the processingdevice further performs the operations of: receiving a request for CWNDstatistics from the client device comprising one or more calculated CWNDvalues; and transmitting the CWND statistics to the client device. 17.The CDN device of claim 16 wherein the CWND statistics comprise at leastone of a maximum CWND value, a minimum CWND value, an average CWNDvalue, and a last of a CWND value.
 18. A content delivery network (CDN)comprising: a first content server configured to: set a congestionwindow (CWND) value for a first communication session between the clientdevice and the first content server; control the CWND value during aduration of the first communication session based at least on a detectedcongestion on a connection between the client device and the firstcontent server; receive a request for CWND statistics from the clientdevice comprising one or more controlled CWND values; and transmit theCWND statistics to the client device; and a second content serverconfigured to: receive a request for content at the second contentserver from the client device, the request comprising an identificationof the content and the CWND statistics; and set an initial CWND valuefor a second communication session between the client device and thesecond content server based at least on the received CWND statistics.19. The CDN of claim 18 wherein the CWND statistics comprise at leastone of a maximum CWND value, a minimum CWND value, an average CWNDvalue, and a last of a CWND value the first communication session. 20.The CDN of claim 18, wherein the request for the CWND statistics isreceived from the client device at the end of the first communicationsession.